CA2193055A1 - Process for the manufacture of thioglycolic acid - Google Patents
Process for the manufacture of thioglycolic acidInfo
- Publication number
- CA2193055A1 CA2193055A1 CA002193055A CA2193055A CA2193055A1 CA 2193055 A1 CA2193055 A1 CA 2193055A1 CA 002193055 A CA002193055 A CA 002193055A CA 2193055 A CA2193055 A CA 2193055A CA 2193055 A1 CA2193055 A1 CA 2193055A1
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- Prior art keywords
- accordance
- conversion
- acid
- hydrogen sulfide
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-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C319/00—Preparation of thiols, sulfides, hydropolysulfides or polysulfides
- C07C319/02—Preparation of thiols, sulfides, hydropolysulfides or polysulfides of thiols
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C319/00—Preparation of thiols, sulfides, hydropolysulfides or polysulfides
- C07C319/02—Preparation of thiols, sulfides, hydropolysulfides or polysulfides of thiols
- C07C319/04—Preparation of thiols, sulfides, hydropolysulfides or polysulfides of thiols by addition of hydrogen sulfide or its salts to unsaturated compounds
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C319/00—Preparation of thiols, sulfides, hydropolysulfides or polysulfides
- C07C319/26—Separation; Purification; Stabilisation; Use of additives
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C323/00—Thiols, sulfides, hydropolysulfides or polysulfides substituted by halogen, oxygen or nitrogen atoms, or by sulfur atoms not being part of thio groups
- C07C323/50—Thiols, sulfides, hydropolysulfides or polysulfides substituted by halogen, oxygen or nitrogen atoms, or by sulfur atoms not being part of thio groups containing thio groups and carboxyl groups bound to the same carbon skeleton
- C07C323/51—Thiols, sulfides, hydropolysulfides or polysulfides substituted by halogen, oxygen or nitrogen atoms, or by sulfur atoms not being part of thio groups containing thio groups and carboxyl groups bound to the same carbon skeleton having the sulfur atoms of the thio groups bound to acyclic carbon atoms of the carbon skeleton
- C07C323/52—Thiols, sulfides, hydropolysulfides or polysulfides substituted by halogen, oxygen or nitrogen atoms, or by sulfur atoms not being part of thio groups containing thio groups and carboxyl groups bound to the same carbon skeleton having the sulfur atoms of the thio groups bound to acyclic carbon atoms of the carbon skeleton the carbon skeleton being acyclic and saturated
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
A process is described for the manufacture of thioglycolic acid by the conversion of monochloroacetic acid with hydro-gen sulfide under pressure in the presence of tertiary amines in solution, whereby care is taken that the partial pressure of hydrogen sulfide over the reaction medium is at least 2 bar up to the end of the reaction, and the thiogly-colic acid formed as an ammonium salt is released by means of acid. The partial pressure of hydrogen sulfide can be maintained by linking the reaction chamber with a source of hydrogen sulfide under pressure during the conversion.
Description
2 1 93û55 Process for the manufacture of thioglycolic acid Akzo Nobel nv, Arnhem * ~ ~
Description:
The invention relates to a process for the manufacture of thioglycolic acid from monochloroacetic acid and hydrogen sulfide.
Thioglycolic acid, also known as mercaptoacetic acid, is a chemical which has a variety of uses, primarily in the form of its salts and esters. For instance, thioglycolates are employed in cold-waving lotions in hair treatment, among other things they are used in permanent deformation of woolens; isooctyl thioglycolate is used for the formation of PVC stabilizers which contain tin, thioglycolic acid es-ters are also used as antioxidants in the rubber industry.
The manufacture of thioglycolic acid is primarily conducted by the reaction of monochloroacetic acid or its salts with hydrogen sulfides such as potassium or sodium hydrogen sul-fide.
The reaction of the hydrogen sulfide such as sodium or am-monium hydrogen sulfide with the monochloroacetic acid can also be conducted by passing hydrogen sulfide into an aque-ous solution of monochloroacetic acid and sodium or ammo-nium hydroxide, as described for example in DE-AS 2 354 098.
The disadvantage of processes of this kind is that not in-considerable quantities of undesired by-products are pro-duced and above all that, according to the following reac-tion equation, sodium chloride or ammonium chloride, re-spectively, is produced as a waste product which must be disposed of.
Cl-CH2COONa + NaSH ----> HS-CH2COONa + NaCl (1) Quite apart from that fact that here, too, not inconsider-able quantities of by-products are formed, the process de-scribed in DE-OS 2 711 867, in which this conversion takes place under a high partial pressure of carbon dioxide, can-not remedy the disadvantage of the formation of sodium chloride either.
Processes have also been made known in which chloroacetic acid is directly converted with hydrogen sulfide. For in-stance, according to the SU patent specification 740.761 chloroacetic acid is converted with hydrogen sulfide at temperatures of 520 to 620 C at atmospheric pressure.
Apart from the fact that there are disadvantages involved in working at such high temperatures, the only 90 % yield also leaves much to be desired. In addition, our own ex-periments have shown that a considerable proportion of by-products which can only be removed with difficulty is formed, such as thiodiglycolic acid or dithiodiglycolic acid.
The US patent specification 4 082 790 describes a process for the manufacture of mercaptans in which an organic chlo-ride or bromide is converted under autogenic pressure with a mixture of hydrogen sulfide and ammonia or an amine. A
disadvantage of this process are the frequently very long 21 ~3055 reaction times which last from several hours to the magni-tude of one day; in addition, working in a closed autoclave is awkward.
From the list in column 2 of this patent specification it can be gathered that a large number of substances contain-ing chlorine or bromine can be converted. Apart from alkyl chlorides such as methyl, ethyl chloride etc., halogenated ethers, ketones etc., a series of halogenated carboxylic acids including chloroacetic acid are also named.
A large number of primary amines with methylamine, buty-lamine etc., secondary amines such as dimethylamine, dipro-pylamine etc., and tertiary amines such as trimethylamine, triethylamine or ethyldimethylamine are recommended aside from ammonia as the base in the reaction. The manufacture of thioglycolic acid from chloroacetic acid is not men-tioned in the examples. What is also missing is any infor-mation on the conditions under which this particular sub-stance can advantageously be converted.
Although a whole series of processes by which thioglycolic acid can be manufactured from chloroacetic acid is now known, the need remains for an improved, economical process for the manufacture of thioglycolic acid which takes the interests of the environment into account.
The object of the invention is therefore to make available a process which works with high selectivities, i.e. a proc-ess in which no, or only small quantities of, by-products are formed and in which no inorganic waste products such as sodium chloride or potassium chloride are formed.
``- 2 1 ~3055 A further object of the invention is to make available a process for which short reaction times suffice and which is particularly suitable for continuous execution.
This task is solved by a process for the manufacture of thioglycolic acid by the conversion of monochloroacetic acid with hydrogen sulfide under pressure in the presence of tertiary amines in solution, whereby care is taken that the partial pressure of hydrogen sulfide over the reaction medium is at least 2 bar up to the end of the reaction, and the thioglycolic acid formed as an ammonium salt is re-leased by means of acid.
The partial pressure of hydrogen sulfide can be maintained during the conversion in advantageous manner by linking the reaction chamber with a source of hydrogen sulfide under pressure.
The partial pressure of hydrogen sulfide is preferably over 2 bar and it is an advantage if it is between 10 and 20 bar.
The reaction can be conducted advantageously at room tem-perature or slightly raised temperatures, i.e. at tempera-tures between 15 and 40 C.
In a further especially favorable embodiment of the process in accordance with the invention the conversion is con-ducted from beginning to end under a constant partial pres-sure of hydrogen sulfide of at least 2 bar.
In a further particularly favorable embodiment of the proc-ess in accordance with the invention trimethylamine is em-ployed as the tertiary alkylamine.
It is beneficial for the conversion to be conducted in the present of about 2 to 2.5 mol tertiary amine per mol monochloroacetic acid. Most suitable for the conversion is monochloroacetic acid dissolved in water. It is an advan-tage to conduct the conversion in homogeneous aqueous solu-tion, i.e. such that both the starting substances and the substances formed remain dissolved in water. In this case the conversion is beneficially conducted at 10 to 60 C, particularly between 30 and 40C.
The conversion can also be conducted in an organic solvent or in a mixture of organic solvents. Methyl t-butyl ether and diisobutyl ketone may be named as examples of suitable solvents.
To release the thioglycolic acid, the use of hydrochloric acid is preferred.
The manufacture of thioglycolic acid can be performed in the following manner. Monochloroacetic acid is dissolved in water, and in addition, in a separate step, a solution of trimethylamine and water is first saturated with hydrogen sulfide and the desired partial pressure of hydrogen sul-fide is set; the concentration of water can vary here over a wide range. It is preferable to have a 15 to 60 % concen-tration of water based on the total reaction mixture. Par-ticularly beneficial are concentrations of water which al-low the reaction to be conducted from beginning to end in a homogeneous phase, i.e. in solution, that means a concen-tration at which both the starting substances and the end product formed are soluble. When trimethylamine is used, for example, this is in the range of about 40 to 50 % by weight of water.
`" 2 1 ~3055 It is obvious that the concentration of water is also de-pendent on the tertiary amine used and the reaction tem-perature.
Therefore, by saturation under pressure a partial pressure of hydrogen sulfide can be set which is so high that it is at least 2 bar throughout the reaction time, without having to pass additional fresh hydrogen sulfide into the reaction chamber during the conversion.
The monochloroacetic acid dissolved in water is then me-tered into the trimethylamine solution which has been satu-rated with hydrogen sulfide and is under the desired par-tial pressure of hydrogen sulfide. Naturally it is also possible, however, to meter the aqueous trimethylamine so-lution into a receiver of monochloroacetic acid under hy-drogen sulfide.
In principle any tertiary amine can be used, whereby short-chain tertiary alkylamines such as triethylamine are pre-ferred.
Most particularly advantageous is the use of trimethy-lamine, particularly on the grounds that the trimethylamine hydrochloride formed in the conversion is a valuable sal-able product.
The reaction temperature, too, can be varied over a wide range and is preferably in the range of about 10 to 60 C, although naturally, higher or lower temperatures are also possible. The temperature range of 30 to 40 C is espe-cially favorable.
`~ 2 1 93055 The ratio of trimethylamine to monochloroacetic acid ought generally to be at least 1.5 : 1 mol.
However, it is preferable to employ quantities of reactants according to the following reaction equation which are stoichiometric or slightly hyperstoichiometric, i.e. the ratio of tertiary amine to monochloroacetic acid is 2 : 1 to 2.5 : 1, and preferably 2.1 to 2.2 : 1.
~3 Cl-CH2-COOH+2(CH3)3N+H2S->HS-CH2-COO (CH3)3HN+(CH3)3N.HCl (1) A further beneficial embodiment consists of making sure that during the conversion the reaction vessel or the reac-tion chamber respectively is linked to a source of hydrogen sulfide at above atmospheric pressure. This can be effected for example by linking a reaction vessel via a feed line with a reservoir containing hydrogen sulfide at above at-mospheric pressure. The hydrogen sulfide at above atmos-pheric pressure can be fed in above the reaction medium, especially above the reaction liquid, but it is also possi-ble to feed in the hydrogen sulfide via a tube or a suit-able feed line using a jet.
In an especially advantageous embodiment the above atmos-pheric partial pressure of hydrogen sulfide is kept con-stant throughout the reaction time.
Separation of the reaction ~roducts:
According to the above reaction equation the desired prod-uct is present in the form of its trimethyl ammonium salt.
In order to-obtain the thioglycolic acid in the form of free acid, after the reaction vessel has relaxed a corre-21 9305~
sponding quantity of hydrochloric acid is added to the re-action mixture, causing the formation of free thioglycolic acid and a second mol of trimethylamine hydrochloride. The thioglycolic acid can be separated without difficulty by extraction from the aqueous solution. Suitable extracting agents are ethers, ketones, especially methyl tert-butyl ether MTBE, t-Amyl methyl ether TAME, diisobutyl ketone. In the next separation step the extracting agent is distilled off and can thus be re-used for extraction. The final proc-essing step consists of the purification of the thiogly-colic acid by distillation.
The following reaction equation expresses the release of the thioglycolic acid salt formed according to (1).
HS-CH2-COO (CH3)3HN+HCl->HS-CH2-COOH+(CH3)3N HCl (2) It was especially surprising to find that in the process in accordance with the invention relatively few by-products are formed, even if higher concentrations of the starting substances are employed. This was not expected, since in the known reactions in which a salt of the monochloroacetic acid is converted with a hydrogen sulfide such as sodium hydrogen sulfide or potassium hydrogen sulfide, with in-creased concentrations the proportion of by-products such as thiodiglycolic and dithiodiglycolic acid also increases sharply. In the process in accordance with the invention, on the other hand, the selectivity remains very high even in concentrated solution.
It is also not necessary to work with high hydrogen sulfide pressures.-~ery high selectivities can also be achieved with low H2S pressures e.g. 5 bar.
21 ~3055 Especially when trimethylamine is used the process in ac-cordance with the invention is free of waste. I.e. thiogly-colic acid and trimethylamine hydrochloride are produced, both of which are valuable products, which can be used di-rectly. The process is thus free of waste, as is seen in the above reaction equation.
Even when other tertiary amines are used, working up is easily possible without inorganic waste products being pro-duced as is the case in conventional processes, e.g. when trioctylamine is used the HCl salt formed can be broken down thermally into HCl gas and amine.
The process enables thioglycolic acid of high purity to be manufactured, so that the product per se can be directly employed or can be transformed directly into the desired secondary products such as salts or esters etc.
The process in accordance with the invention is especially suitable for continuous execution.
Because of the high reaction rate this process is also ex-cellently well suited to continuous process execution in a cascade of stirred tanks. The efficient reaction system means that only a few stirred tanks are required to bring about the complete conversion of the monochloroacetic acid to thioglycolic acid.
Steel autoclaves are employed which are equipped with an effective agitator and a pressure control or pressure regu-lator mechanism. The agitated autoclaves are arranged such that first the complete conversion of monochloroacetic acid to the trimethyl ammonium salt of the thioglycolic acid and then the release of the thioglycolic acid with hydrochloric 1() acid takes place. Separation of the products also takes place continuously, as described above.
The invention will be explained in more detail using the following examples:
Example 1 216.7 g aqueous trimethylamine solution is placed in a 1 liter Buchi steel autoclave, whereby the content of tri-methylamine is 45 % (1.65 mol trimethylamine). This solu-tion is then saturated with hydrogen sulfide until the de-sired pressure of 15 bar has been reached. The temperature is set to 40 C with the aid of a thermostat and the re-ceiver mixed through with a gas dispersion agitator at 700 r.p.m. The reaction begins when the 70.9 g monochloroacetic acid (0.75 mol) dissolved in 100 g water is metered into the reaction vessel within a minute with the aid of a pis-ton pump. During~the reaction the pressure and temperature are regulated. After 10 minutes the monochloroacetic acid has been completely converted and a 96.0 % yield of thio-glycolic acid has been achieved.
Example 2 Execution as in Example 1, but at 20 C. After 30 minutes the monochloroacetic acid has been completely converted and the yield of thioglycolic acid is 97.5 %.
Example 3 Execution as in Example 1, but with 207.8 g aqueous trieth-ylamine solution (152.0 g triethylamine + 55.8 g water).
2 ~ ~3055 After 30 minutes the monochloroacetic acid has been com-pletely converted and the yield of thioglycolic acid is 94.5 %.
.
Example 4 Execution as in Example 1, but at 5 bar hydrogen sulfide.
After 30 minutes the monochloroacetic acid has been com-pletely converted and the yield of thioglycolic acid is 94.0 %.
Example S
Execution as in Example 1, but with only 1.05 mol trimethy-lamine (mol ratio of trimethylamine to monochloroacetic acid = 1.5 : 1). After 120 minutes the monochloroacetic acid has been completely converted with an 80% yield of thioglycolic acid.
Example 6 197 g aqueous trimethylamine solution is placed in a 1 li-ter Buchi steel autoclave, whereby the content of trimethy-lamine is 45 %. This solution is then saturated with hydro-gen sulfide until the desired pressure of 15 bar has been reached. The autoclave is then separated from the hydrogen sulfide supply. The temperature is set to 30 C with the aid of a thermostat and the receiver mixed through with a gas dispersion agitator at 700 r.p.m.
The reaction begins when the 70.9 g monochloroacetic acid (0.75 mol) dissolved in 100 g water is metered into the re-action vessel within a minute with the aid of a piston -pump. By the metering of the monochloroacetic acid part of the hydrogen sulfide bound in the solution is released, by means of which the pressure in the reaction chamber in-creases to 25 bar. At the end of the reaction the partial pressure of hydrogen sulfide is 23 bar.
After 30 minutes the monochloroacetic acid has been com-pletely converted and a 96.7 % yield of thioglycolic acid has been achieved.
Example 7 192 g methyl tert-butyl ether MTBE and 39 g anhydrous trimethylamine are placed in a 1 liter Buchi steel auto-clave. This solution is then saturated with hydrogen sul-fide until the desired pressure of 10 bar has been reached.
The temperature is set to 20 C with the aid of a thermo-stat and the receiver mixed through with a gas dispersion agitator at 700 r.p.m.
The reaction begins when the 28.4 g monochloroacetic acid dissolved in 60 g methyl tert-butyl ether MTBE is metered into the reaction vessel within a minute with the aid of a piston pump. After 20 minutes the monochloroacetic acid has been completely converted and a 92.0 % yield of thiogly-colic acid has been achieved.
Example 8 Execution as in Example 7, but in place of MTBE diisobutyl ketone DIBK is used as the solvent. After 25 minutes the monochloroacetic acid has been completely converted, the yield of thioglycolic acid is 91 %.
Description:
The invention relates to a process for the manufacture of thioglycolic acid from monochloroacetic acid and hydrogen sulfide.
Thioglycolic acid, also known as mercaptoacetic acid, is a chemical which has a variety of uses, primarily in the form of its salts and esters. For instance, thioglycolates are employed in cold-waving lotions in hair treatment, among other things they are used in permanent deformation of woolens; isooctyl thioglycolate is used for the formation of PVC stabilizers which contain tin, thioglycolic acid es-ters are also used as antioxidants in the rubber industry.
The manufacture of thioglycolic acid is primarily conducted by the reaction of monochloroacetic acid or its salts with hydrogen sulfides such as potassium or sodium hydrogen sul-fide.
The reaction of the hydrogen sulfide such as sodium or am-monium hydrogen sulfide with the monochloroacetic acid can also be conducted by passing hydrogen sulfide into an aque-ous solution of monochloroacetic acid and sodium or ammo-nium hydroxide, as described for example in DE-AS 2 354 098.
The disadvantage of processes of this kind is that not in-considerable quantities of undesired by-products are pro-duced and above all that, according to the following reac-tion equation, sodium chloride or ammonium chloride, re-spectively, is produced as a waste product which must be disposed of.
Cl-CH2COONa + NaSH ----> HS-CH2COONa + NaCl (1) Quite apart from that fact that here, too, not inconsider-able quantities of by-products are formed, the process de-scribed in DE-OS 2 711 867, in which this conversion takes place under a high partial pressure of carbon dioxide, can-not remedy the disadvantage of the formation of sodium chloride either.
Processes have also been made known in which chloroacetic acid is directly converted with hydrogen sulfide. For in-stance, according to the SU patent specification 740.761 chloroacetic acid is converted with hydrogen sulfide at temperatures of 520 to 620 C at atmospheric pressure.
Apart from the fact that there are disadvantages involved in working at such high temperatures, the only 90 % yield also leaves much to be desired. In addition, our own ex-periments have shown that a considerable proportion of by-products which can only be removed with difficulty is formed, such as thiodiglycolic acid or dithiodiglycolic acid.
The US patent specification 4 082 790 describes a process for the manufacture of mercaptans in which an organic chlo-ride or bromide is converted under autogenic pressure with a mixture of hydrogen sulfide and ammonia or an amine. A
disadvantage of this process are the frequently very long 21 ~3055 reaction times which last from several hours to the magni-tude of one day; in addition, working in a closed autoclave is awkward.
From the list in column 2 of this patent specification it can be gathered that a large number of substances contain-ing chlorine or bromine can be converted. Apart from alkyl chlorides such as methyl, ethyl chloride etc., halogenated ethers, ketones etc., a series of halogenated carboxylic acids including chloroacetic acid are also named.
A large number of primary amines with methylamine, buty-lamine etc., secondary amines such as dimethylamine, dipro-pylamine etc., and tertiary amines such as trimethylamine, triethylamine or ethyldimethylamine are recommended aside from ammonia as the base in the reaction. The manufacture of thioglycolic acid from chloroacetic acid is not men-tioned in the examples. What is also missing is any infor-mation on the conditions under which this particular sub-stance can advantageously be converted.
Although a whole series of processes by which thioglycolic acid can be manufactured from chloroacetic acid is now known, the need remains for an improved, economical process for the manufacture of thioglycolic acid which takes the interests of the environment into account.
The object of the invention is therefore to make available a process which works with high selectivities, i.e. a proc-ess in which no, or only small quantities of, by-products are formed and in which no inorganic waste products such as sodium chloride or potassium chloride are formed.
``- 2 1 ~3055 A further object of the invention is to make available a process for which short reaction times suffice and which is particularly suitable for continuous execution.
This task is solved by a process for the manufacture of thioglycolic acid by the conversion of monochloroacetic acid with hydrogen sulfide under pressure in the presence of tertiary amines in solution, whereby care is taken that the partial pressure of hydrogen sulfide over the reaction medium is at least 2 bar up to the end of the reaction, and the thioglycolic acid formed as an ammonium salt is re-leased by means of acid.
The partial pressure of hydrogen sulfide can be maintained during the conversion in advantageous manner by linking the reaction chamber with a source of hydrogen sulfide under pressure.
The partial pressure of hydrogen sulfide is preferably over 2 bar and it is an advantage if it is between 10 and 20 bar.
The reaction can be conducted advantageously at room tem-perature or slightly raised temperatures, i.e. at tempera-tures between 15 and 40 C.
In a further especially favorable embodiment of the process in accordance with the invention the conversion is con-ducted from beginning to end under a constant partial pres-sure of hydrogen sulfide of at least 2 bar.
In a further particularly favorable embodiment of the proc-ess in accordance with the invention trimethylamine is em-ployed as the tertiary alkylamine.
It is beneficial for the conversion to be conducted in the present of about 2 to 2.5 mol tertiary amine per mol monochloroacetic acid. Most suitable for the conversion is monochloroacetic acid dissolved in water. It is an advan-tage to conduct the conversion in homogeneous aqueous solu-tion, i.e. such that both the starting substances and the substances formed remain dissolved in water. In this case the conversion is beneficially conducted at 10 to 60 C, particularly between 30 and 40C.
The conversion can also be conducted in an organic solvent or in a mixture of organic solvents. Methyl t-butyl ether and diisobutyl ketone may be named as examples of suitable solvents.
To release the thioglycolic acid, the use of hydrochloric acid is preferred.
The manufacture of thioglycolic acid can be performed in the following manner. Monochloroacetic acid is dissolved in water, and in addition, in a separate step, a solution of trimethylamine and water is first saturated with hydrogen sulfide and the desired partial pressure of hydrogen sul-fide is set; the concentration of water can vary here over a wide range. It is preferable to have a 15 to 60 % concen-tration of water based on the total reaction mixture. Par-ticularly beneficial are concentrations of water which al-low the reaction to be conducted from beginning to end in a homogeneous phase, i.e. in solution, that means a concen-tration at which both the starting substances and the end product formed are soluble. When trimethylamine is used, for example, this is in the range of about 40 to 50 % by weight of water.
`" 2 1 ~3055 It is obvious that the concentration of water is also de-pendent on the tertiary amine used and the reaction tem-perature.
Therefore, by saturation under pressure a partial pressure of hydrogen sulfide can be set which is so high that it is at least 2 bar throughout the reaction time, without having to pass additional fresh hydrogen sulfide into the reaction chamber during the conversion.
The monochloroacetic acid dissolved in water is then me-tered into the trimethylamine solution which has been satu-rated with hydrogen sulfide and is under the desired par-tial pressure of hydrogen sulfide. Naturally it is also possible, however, to meter the aqueous trimethylamine so-lution into a receiver of monochloroacetic acid under hy-drogen sulfide.
In principle any tertiary amine can be used, whereby short-chain tertiary alkylamines such as triethylamine are pre-ferred.
Most particularly advantageous is the use of trimethy-lamine, particularly on the grounds that the trimethylamine hydrochloride formed in the conversion is a valuable sal-able product.
The reaction temperature, too, can be varied over a wide range and is preferably in the range of about 10 to 60 C, although naturally, higher or lower temperatures are also possible. The temperature range of 30 to 40 C is espe-cially favorable.
`~ 2 1 93055 The ratio of trimethylamine to monochloroacetic acid ought generally to be at least 1.5 : 1 mol.
However, it is preferable to employ quantities of reactants according to the following reaction equation which are stoichiometric or slightly hyperstoichiometric, i.e. the ratio of tertiary amine to monochloroacetic acid is 2 : 1 to 2.5 : 1, and preferably 2.1 to 2.2 : 1.
~3 Cl-CH2-COOH+2(CH3)3N+H2S->HS-CH2-COO (CH3)3HN+(CH3)3N.HCl (1) A further beneficial embodiment consists of making sure that during the conversion the reaction vessel or the reac-tion chamber respectively is linked to a source of hydrogen sulfide at above atmospheric pressure. This can be effected for example by linking a reaction vessel via a feed line with a reservoir containing hydrogen sulfide at above at-mospheric pressure. The hydrogen sulfide at above atmos-pheric pressure can be fed in above the reaction medium, especially above the reaction liquid, but it is also possi-ble to feed in the hydrogen sulfide via a tube or a suit-able feed line using a jet.
In an especially advantageous embodiment the above atmos-pheric partial pressure of hydrogen sulfide is kept con-stant throughout the reaction time.
Separation of the reaction ~roducts:
According to the above reaction equation the desired prod-uct is present in the form of its trimethyl ammonium salt.
In order to-obtain the thioglycolic acid in the form of free acid, after the reaction vessel has relaxed a corre-21 9305~
sponding quantity of hydrochloric acid is added to the re-action mixture, causing the formation of free thioglycolic acid and a second mol of trimethylamine hydrochloride. The thioglycolic acid can be separated without difficulty by extraction from the aqueous solution. Suitable extracting agents are ethers, ketones, especially methyl tert-butyl ether MTBE, t-Amyl methyl ether TAME, diisobutyl ketone. In the next separation step the extracting agent is distilled off and can thus be re-used for extraction. The final proc-essing step consists of the purification of the thiogly-colic acid by distillation.
The following reaction equation expresses the release of the thioglycolic acid salt formed according to (1).
HS-CH2-COO (CH3)3HN+HCl->HS-CH2-COOH+(CH3)3N HCl (2) It was especially surprising to find that in the process in accordance with the invention relatively few by-products are formed, even if higher concentrations of the starting substances are employed. This was not expected, since in the known reactions in which a salt of the monochloroacetic acid is converted with a hydrogen sulfide such as sodium hydrogen sulfide or potassium hydrogen sulfide, with in-creased concentrations the proportion of by-products such as thiodiglycolic and dithiodiglycolic acid also increases sharply. In the process in accordance with the invention, on the other hand, the selectivity remains very high even in concentrated solution.
It is also not necessary to work with high hydrogen sulfide pressures.-~ery high selectivities can also be achieved with low H2S pressures e.g. 5 bar.
21 ~3055 Especially when trimethylamine is used the process in ac-cordance with the invention is free of waste. I.e. thiogly-colic acid and trimethylamine hydrochloride are produced, both of which are valuable products, which can be used di-rectly. The process is thus free of waste, as is seen in the above reaction equation.
Even when other tertiary amines are used, working up is easily possible without inorganic waste products being pro-duced as is the case in conventional processes, e.g. when trioctylamine is used the HCl salt formed can be broken down thermally into HCl gas and amine.
The process enables thioglycolic acid of high purity to be manufactured, so that the product per se can be directly employed or can be transformed directly into the desired secondary products such as salts or esters etc.
The process in accordance with the invention is especially suitable for continuous execution.
Because of the high reaction rate this process is also ex-cellently well suited to continuous process execution in a cascade of stirred tanks. The efficient reaction system means that only a few stirred tanks are required to bring about the complete conversion of the monochloroacetic acid to thioglycolic acid.
Steel autoclaves are employed which are equipped with an effective agitator and a pressure control or pressure regu-lator mechanism. The agitated autoclaves are arranged such that first the complete conversion of monochloroacetic acid to the trimethyl ammonium salt of the thioglycolic acid and then the release of the thioglycolic acid with hydrochloric 1() acid takes place. Separation of the products also takes place continuously, as described above.
The invention will be explained in more detail using the following examples:
Example 1 216.7 g aqueous trimethylamine solution is placed in a 1 liter Buchi steel autoclave, whereby the content of tri-methylamine is 45 % (1.65 mol trimethylamine). This solu-tion is then saturated with hydrogen sulfide until the de-sired pressure of 15 bar has been reached. The temperature is set to 40 C with the aid of a thermostat and the re-ceiver mixed through with a gas dispersion agitator at 700 r.p.m. The reaction begins when the 70.9 g monochloroacetic acid (0.75 mol) dissolved in 100 g water is metered into the reaction vessel within a minute with the aid of a pis-ton pump. During~the reaction the pressure and temperature are regulated. After 10 minutes the monochloroacetic acid has been completely converted and a 96.0 % yield of thio-glycolic acid has been achieved.
Example 2 Execution as in Example 1, but at 20 C. After 30 minutes the monochloroacetic acid has been completely converted and the yield of thioglycolic acid is 97.5 %.
Example 3 Execution as in Example 1, but with 207.8 g aqueous trieth-ylamine solution (152.0 g triethylamine + 55.8 g water).
2 ~ ~3055 After 30 minutes the monochloroacetic acid has been com-pletely converted and the yield of thioglycolic acid is 94.5 %.
.
Example 4 Execution as in Example 1, but at 5 bar hydrogen sulfide.
After 30 minutes the monochloroacetic acid has been com-pletely converted and the yield of thioglycolic acid is 94.0 %.
Example S
Execution as in Example 1, but with only 1.05 mol trimethy-lamine (mol ratio of trimethylamine to monochloroacetic acid = 1.5 : 1). After 120 minutes the monochloroacetic acid has been completely converted with an 80% yield of thioglycolic acid.
Example 6 197 g aqueous trimethylamine solution is placed in a 1 li-ter Buchi steel autoclave, whereby the content of trimethy-lamine is 45 %. This solution is then saturated with hydro-gen sulfide until the desired pressure of 15 bar has been reached. The autoclave is then separated from the hydrogen sulfide supply. The temperature is set to 30 C with the aid of a thermostat and the receiver mixed through with a gas dispersion agitator at 700 r.p.m.
The reaction begins when the 70.9 g monochloroacetic acid (0.75 mol) dissolved in 100 g water is metered into the re-action vessel within a minute with the aid of a piston -pump. By the metering of the monochloroacetic acid part of the hydrogen sulfide bound in the solution is released, by means of which the pressure in the reaction chamber in-creases to 25 bar. At the end of the reaction the partial pressure of hydrogen sulfide is 23 bar.
After 30 minutes the monochloroacetic acid has been com-pletely converted and a 96.7 % yield of thioglycolic acid has been achieved.
Example 7 192 g methyl tert-butyl ether MTBE and 39 g anhydrous trimethylamine are placed in a 1 liter Buchi steel auto-clave. This solution is then saturated with hydrogen sul-fide until the desired pressure of 10 bar has been reached.
The temperature is set to 20 C with the aid of a thermo-stat and the receiver mixed through with a gas dispersion agitator at 700 r.p.m.
The reaction begins when the 28.4 g monochloroacetic acid dissolved in 60 g methyl tert-butyl ether MTBE is metered into the reaction vessel within a minute with the aid of a piston pump. After 20 minutes the monochloroacetic acid has been completely converted and a 92.0 % yield of thiogly-colic acid has been achieved.
Example 8 Execution as in Example 7, but in place of MTBE diisobutyl ketone DIBK is used as the solvent. After 25 minutes the monochloroacetic acid has been completely converted, the yield of thioglycolic acid is 91 %.
Claims (18)
1. Process for the manufacture of thioglycolic acid by the conversion of monochloroacetic acid with hydrogen sul-fide under pressure in the presence of tertiary amines in solution, whereby care is taken that the partial pressure of hydrogen sulfide over the reaction medium is at least 2 bar, and the thioglycolic acid formed as an ammonium salt is released by means of acid.
2. Process in accordance with Claim 1, characterized in that the partial pressure of hydrogen sulfide is main-tained by means of linking the reaction chamber with a source of hydrogen sulfide under pressure during the conversion.
3. Process in accordance with Claim 1 or 2, characterized in that the partial pressure of hydrogen sulfide is more than 2 bar.
4. Process in accordance with Claim 3, characterized in that the partial pressure of hydrogen sulfide is 10 to 20 bar.
5. Process in accordance with one of Claims 1 to 4, char-acterized in that the conversion is conducted at 15 to 40 °C.
6. Process in accordance with one of Claims 1 to 5, char-acterized in that the conversion is conducted from be-ginning to end under a constant partial pressure of hy-drogen sulfide.
7. Process in accordance with one of Claims 1 to 6, char-acterized in that tertiary alkylamines are used.
8. Process in accordance with Claim 7, characterized in that trimethylamine is used as the tertiary alkylamine.
9. Process in accordance with one of Claims 1 to 8, char-acterized in that the conversion is conducted in the presence of 1.5 to 2.5 mol, preferably 2.1 to 2.2 mol of tertiary amine per mol of monochloroacetic acid.
10. Process in accordance with one or more of Claims 1 to 9, characterized in that aqueous monochloroacetic acid is used in the conversion.
11. Process in accordance with one or more of Claims 1 to 10, characterized in that the conversion is conducted in homogeneous aqueous solution.
12. Process in accordance with one or more of Claims 1 to 9, characterized in that the conversion is conducted in an organic solvent.
13. Process in accordance with Claim 12, characterized in that the conversion is conducted in a mixture of or-ganic solvents.
14. Process in accordance with one or more of Claims 1 to 13, characterized in that the conversion is conducted at temperatures of 10 to 60 °C.
15. Process in accordance with Claim 14, characterized in that the conversion is conducted at temperatures of 30 to 40 °C.
16. Process in accordance with one or more of Claims 1 to 15, characterized in that the conversion is conducted with a partial pressure of hydrogen sulfide of 5 to 40 bar.
17. Process in accordance with one or more of Claims 1 to 16, characterized in that the conversion is conducted continuously.
18. Process in accordance with one or more of Claims 1 to 17, characterized in that hydrochloric acid is employed to release the thioglycolic acid.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19547867 | 1995-12-21 | ||
| DE19547867.3 | 1995-12-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2193055A1 true CA2193055A1 (en) | 1997-06-22 |
Family
ID=7780834
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002193055A Abandoned CA2193055A1 (en) | 1995-12-21 | 1996-12-16 | Process for the manufacture of thioglycolic acid |
Country Status (11)
| Country | Link |
|---|---|
| EP (1) | EP0780368B1 (en) |
| JP (1) | JPH09176110A (en) |
| KR (1) | KR970042496A (en) |
| AT (1) | ATE182329T1 (en) |
| CA (1) | CA2193055A1 (en) |
| CZ (1) | CZ291583B6 (en) |
| DE (1) | DE59602478D1 (en) |
| ES (1) | ES2135836T3 (en) |
| PL (1) | PL185231B1 (en) |
| SK (1) | SK282089B6 (en) |
| TW (1) | TW430643B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20090281269A1 (en) | 2006-04-21 | 2009-11-12 | Mitsui Chemicals, Inc. | Process for producing pentaerythritol mercaptocarboxylic esters and polymerizable compositions containing the esters |
| EP3222621B1 (en) | 2010-08-17 | 2023-03-08 | 3M Innovative Properties Company | Lipidated immune response modifier compound and its medical use |
| JP2019178085A (en) * | 2018-03-30 | 2019-10-17 | 三井化学株式会社 | (poly)thiol compound production method |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2354098B2 (en) | 1973-10-29 | 1976-05-13 | Akzo Gmbh, 5600 Wuppertal | METHOD FOR MANUFACTURING MERCAPTOCARBON ACIDS |
| US4082790A (en) | 1974-12-11 | 1978-04-04 | Dow Corning Corporation | Method of preparing mercaptans |
| DE2711867A1 (en) | 1977-03-18 | 1978-09-21 | Hoechst Ag | Thioglycolic acid prepn. - by reacting mono-chloroacetic acid with e.g. Gp=IA or Gp=IIA metal bi:sulphide in aq. medium under carbon di:oxide pressure |
| JPS53147026A (en) * | 1977-05-25 | 1978-12-21 | Denki Kagaku Kogyo Kk | Continuous preparation of thioglycolic acid |
| SU740761A1 (en) | 1978-06-28 | 1980-06-15 | Рубежанский филиал Ворошиловградского машиностроительного института | Method of preparing thioglycolic acid |
| JPS55145663A (en) * | 1979-05-01 | 1980-11-13 | Denki Kagaku Kogyo Kk | Continuous preparation of thioglycolic acid |
| EP0021732B2 (en) * | 1979-06-22 | 1988-04-13 | Vickers Limited | Hydraulic steering gear for ships |
| JPS6036456A (en) * | 1983-08-09 | 1985-02-25 | Santen Pharmaceut Co Ltd | Preparation of disulfide compound |
| NL8502488A (en) * | 1984-09-28 | 1986-04-16 | Grace W R & Co | SYNTHESIS OF THIOGLYCOLIC ACID. |
| US5023371A (en) * | 1986-03-07 | 1991-06-11 | W. R. Grace & Co.-Conn. | Synthesis of thioglycolic acid |
| IE912903A1 (en) * | 1990-09-19 | 1992-02-25 | Atochem North America | Process of manufacturing arylalkyl and alkyl mercaptans |
-
1996
- 1996-12-06 AT AT96119601T patent/ATE182329T1/en not_active IP Right Cessation
- 1996-12-06 EP EP96119601A patent/EP0780368B1/en not_active Expired - Lifetime
- 1996-12-06 ES ES96119601T patent/ES2135836T3/en not_active Expired - Lifetime
- 1996-12-06 DE DE59602478T patent/DE59602478D1/en not_active Expired - Fee Related
- 1996-12-12 TW TW085115354A patent/TW430643B/en active
- 1996-12-13 JP JP8334060A patent/JPH09176110A/en active Pending
- 1996-12-16 CA CA002193055A patent/CA2193055A1/en not_active Abandoned
- 1996-12-18 SK SK1629-96A patent/SK282089B6/en unknown
- 1996-12-18 CZ CZ19963735A patent/CZ291583B6/en not_active IP Right Cessation
- 1996-12-19 KR KR1019960068083A patent/KR970042496A/en active IP Right Grant
- 1996-12-20 PL PL96317632A patent/PL185231B1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| SK162996A3 (en) | 1997-11-05 |
| CZ291583B6 (en) | 2003-04-16 |
| TW430643B (en) | 2001-04-21 |
| EP0780368B1 (en) | 1999-07-21 |
| EP0780368A1 (en) | 1997-06-25 |
| CZ373596A3 (en) | 1998-05-13 |
| JPH09176110A (en) | 1997-07-08 |
| SK282089B6 (en) | 2001-10-08 |
| PL317632A1 (en) | 1997-06-23 |
| DE59602478D1 (en) | 1999-08-26 |
| PL185231B1 (en) | 2003-04-30 |
| ES2135836T3 (en) | 1999-11-01 |
| KR970042496A (en) | 1997-07-24 |
| ATE182329T1 (en) | 1999-08-15 |
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| Date | Code | Title | Description |
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| EEER | Examination request | ||
| FZDE | Discontinued |